As is well-known in the art, certain materials fabrication tools require precision guiding of work pieces thereon to produce desired geometries, tolerances, and configurations. Thus, conventional materials fabrication equipment such as table saws, router tables, band saws, and the like have included at or on guiding surfaces one or more longitudinally disposed slots adapted for mated fitting with guide members that may be guided rectilinearly. The geometries of the guide members must be closely correlated with the dimensions of the slots so as to avoid binding, wobble, or other tracking errors. The dimensions of such slots often conform to industry-wide standards, albeit within a broad range of tolerances. However, dimensional variation within this tolerance range from manufacturer to manufacturer, and from machine to machine often result in a poor fit between a particular guide member and a given slot, thus producing unacceptable occurrences of the aforementioned tracking errors.
To overcome the foregoing problems, there have previously been proposed a variety of configurations including the formation of the guide member in an extended longitudinal geometry that fits within the guiding slots. Due to the aforementioned variations in slot dimensions, however, it was typically necessary to machine the guide member to exacting tolerances to produce a customized fit between the guide member and a particular guide slot and reduce tracking errors. In addition to being relatively expensive to manufacture, such a custom guide member would also become one of a kind, and could not be readily transferred to another machine whose guide slots differed in geometry from those to which it had previously been fitted.
Christopher L. Taylor presented one solution to the aforementioned problem in U.S. Pat. No. 5,275,074. Taylor's '074 patent describes a slider bar constructed from a generally U-shaped channel, whose two legs are sloped like a truncated wedge. Sections of the sides of the slider bar in the '074 patent are separated from the main body to permit them to spring outwardly under pressure from wedging members that are removably connected to the channel using conventional machine screws.
U.S. Pat. No. 5,617,909 issued to Duginske describes another method for obtaining a secure sliding fit between a guide member and a slot. The '909 patent describes a hole bored through the sides of the guide member, which hole is threaded on one side of the member. A bearing is inserted into the unthreaded side of the hole, while a set screw is threaded into the threaded side of the hole. When used on a particular slot of a machine, the set screw is manually adjusted so that the set screw pushes a portion of the bearing out of the hole where it is maintained in abutting relationship with the side of the slot. One obvious limitation in the '909 design is that because the set screw is threaded into the side of the member, it cannot be adjusted with the member in place within the slot. Another limitation of the '909 design is increased fabrication costs due to the need for a separate manufacturing operation required to turn the guide member on its side to machine the aforementioned hole through the sides of the guide member.
Despite successful operation of the slider described in Taylor's '074 patent, a more rigid but equally as effective guide member is required for many operations. The slider in the '074 patent is preferably constructed of extruded aluminum because that material provides the most cost-effective system. While more rigid materials than aluminum could be used for the '074 patent's slider, such a product would be considerably more expensive due to manufacturing and machining costs. Another limitation of the '704 design relates to the need to separate sections of the sides of the guide member from the main body. This not only increases fabrication costs, but also weakens the guide member at the points where the sidewall separations occur.
While both the '704 and '909 designs provide means for adjusting the width of the guide member to conform to the variable widths of different guide slots, they are only partially effective in overcoming alignment errors associated with deviations from perfection in either the straightness or the width geometries of the guide members themselves.
In view of the foregoing, it is apparent that there has continued to be a need for an improved positionable guide member that can operate with a high degree of alignment accuracy over a wide range of guide slot geometries and that can be cost-effectively constructed from a wide variety of materials to provide strength and rigidity necessary for materials fabrication and other operations. Additionally, the need continues for such a guide member that also embodies simplicity of operation, that does not encroach upon equipment working surfaces, and that allows for adjustment to the geometry of a particular guide slot while the guide member is positioned within the slot. There also continues to be a need for a guide member that provides a high degree of alignment accuracy even when the straightness and width geometries of the guide member itself are less than perfect.